There are many computer applications and file sharing websites where the user can add tags or keywords to media items of interest. These mostly work on a flat structure of tags. In this regard, the user can access media items using a browser application by choosing a tag from a list of available tags and then view the set of items with the chosen tag. Such arrangements however have no hierarchy of tags. For large collections with a large number of tags it becomes difficult to manage and browse the available tags.
A few applications designed as professional image management applications, allow the user to organise their tags into a hierarchy or tree structure using drag-and-drop techniques in a manner common to many computer applications. The computer applications are exclusively configured to operate on desktop or substantive computer systems when substantial user control (via keyboard and mouse/pointer for example), graphical display and underlying computer processing power, are available. A drag-and-drop interface is not suited to domestic “living room” environments where a user controllable input device is typically a handheld remote control input device having a limited keypad, and the visual interface, such as a television display, may not be configured for high resolution graphical reproduction.
In an application aimed at professional use in a personal computer environment it is acceptable for the user to have to learn the operational controls and behaviour of the application. However, for the living room environment it is important any user interface be simple and intuitive to use. In the drag-and-drop interface previously described, it can be ambiguous to the user when moving a tag below another tag in the hierarchy what this association of the two tags implies. The association could imply that files tagged with the lower level tag now automatically or implicitly have the higher level tag. Alternatively the association could imply that the browser application will only display items which have both tags when the lower level tag is selected. Other interpretations are also possible.
Another known solution to the problem of providing some organisational structure to a collection of tags is to allow the user to name a group of tags. However these tag groups are not tags themselves. The two concepts of tags and tag groups are independent and the user cannot make a tag into a tag group or vice versa. An item cannot be added to a tag group directly; it must be tagged with a tag in the group. This system does not take advantage of the fact that some tags are more general and some tags more specific. More general tags naturally reside higher in the hierarchy than more specific tags, and more general tags are likely to be found on a larger number of items than specific tags.